Every single reboot on my lower end Motorola phone, they have decided it fit to re-enable com.glance.lockscreenM every single boot and on every single update.
It's horrible. I don't think I can trust them to produce a Graphene phone at all, really, despite all of everyone's assurances.
just use Shizuku + Canta to remove it
At least you can disable it; on some phones (especially Chinese phones) you cannot do anything to the system services, they intercept all app requests, essentially what Google did but with their system. The only recommendation I can give you is to look into Hail (device-owner app that can "freeze" apps, a "lower level" form of disabling, see https://f-droid.org/en/packages/com.aistra.hail/) which will mean even if the app gets reinstalled on system update, the device owner app will prevent it from running.
I think GrapheneOS might have issues in the future considering that Android will be getting more and more locked down. People say GrapheneOS is the better OS when it just is hardened Android; it is doomed purely because of the Android base.
Perhaps a Linux based edition of GrapheneOS would do well, even if it will not have a lot of app compatibility. There's only so much patching you have to do to Android before it just becomes more work than good.